Inhibitors for olefin complexing process

ABSTRACT

Combinations of organic phosphines and organic nitrogen bases help stabilize complexing solutions containing cuprous and silver salts whose anionic components are Lewis acids, said salts being dissolved in aromatic solvents, when the solutions are in the presence of olefins, to prevent side reactions from occurring during olefin complexing processes in which the above complexing solutions are employed.

mites States Patent [191 Horowitz et al.

INHIBITORS FOR OLEFIN COMPLEXING PROCESS Inventors: Hugh II. Horowitz,Elizabeth, N.J.;

Helmut W. Ruhle, Dormagen,

Germany Esso Research and Engineering Company, Linden, NJ.

Filed: June 2, 1972 Appl. No.: 259,219

Assignee:

U.S. CL. 260/677 A, 260/683.15, 260/68l.5 C, 260/666.5

Int. Cl. C07c 11/12, C070 7/00 Field of Search 2601677 A, 683.15,260/681.5 C, 666.5

References Cited UNITED STATES PATENTS 11/1968 Long 260/68L5 C 1451Sept. 11, 1973 Morrell 2610/6815 C 2,566,137 8/1951 Morrcll 260/68L5 C3,265,751 8/1966 McCoy et al. 260/666.5 2,444,945 7/1948 Morrell260/68L5 C Primary Examiner-Delbert E. Gantz Assistant Examiner-JuanitaM. Nelson Attorney-Leon Chasan et al.

571 7 ABSTRACT 11 Claims, No Drawings INHIBITORS FOR OLEFIN COMPLEXINGPROCESS DESCRIPTION OF THE PRIOR ART It is known in the art to usevarious copper and silver salts whose anionic components are Lewis acidssuch as CuPF CuBF,, CuAlCl, and the like and corresponding silver saltsas complexing agents.

However, the use of these salts, when dissolved in aromatic hydrocarbonsolvents, in olefin complexing processes have serious drawbacks makingtheir use less practicable. It is known that these types of materialstend to dissociate in solution yielding Lewis acid moieties such asAlCl, and the like. These Lewis acids when in the presence of smallamounts of HCl and other proton donor materials are known to catalyzealkylation of the aromatics by the olefins and other side reactionsleading to the inactivation of the complex. Hence, the need to minimizeor eliminate these alkylation and side reactions is suitably desired bythe art.

SUMMARY OF THE INVENTION In accordance with the present invention, theaddition of minor amounts of phosphines, in combination with minoramounts of organic nitrogen bases to aromatic solutions containingcomplexing materials such as- CuPF CuBF}, CuBF c l, CuAlCL, CuAlBr Cu-TaF CuAlCl,Br, and the like and their corresponding silver salts, saidsolutions being used in an olefin complexing process, provides increasedstability for said solutions and substantially prevents alkylation ofthe arcmatic by the olefin and olefin polymerization side reactions.

The use of CuAlCh, CuBF, and the like, dissolved in suitable solventssuch as aromatic hydrocarbons in olefin separation-by-complexingprocesses has associated problems which makes their use less practicalin a commercial olefin recovery process. It is known that theseparticular cuprous salts, and equally the corresponding silver salts,dissociate somewhat in solution to yield Lewis acid materials such asMC], and BF, These Lewis acid materials, when in the presence of protondonors such as l-lCl, catalyze alkylation of aromatics by olefins and athigh pressures cause olefin polymerization to occur. Hence, in an olefincomplexing process, where the above-described cuprous and silver saltsare being employed in aromatic solvent materials, alkylation andpolymerization side reactions can be expected to occur.

It has been unexpectedly discovered that the rate of alkylation in theabove-described systems can be substantially reduced by adding to thec'omplexing solutions, in effective amounts, phosphine materials incombination with organic nitrogen base compounds. It is believed thatthe alkylation rates may be reduced in the above manner because of theneutralization of the proton donor material, which is typically l-lCl,and that such neutralization by the organic, nitrogen'bases can occureven in the presence of the Lewis acid moieties such as AlCl,, BF, andthe like. The addition of the phosphine material is believed to addstability to the overall system and allow this neutralization to occurand thereby provide long range stability for the system at a betterlevel than the organic nitrogen additive ent invention include moietiessuch as trialkyl phosphines, alkylaryl phosphines, aralkyl phosphines,benzyl phosphines and materials having the general formula R,R,R,Pwherein R R, and R, are monovalent radicals independently selected fromthe group consisting of alkyl radicals having from one to 20 carbonatoms, preferably from two to 10 carbon atoms; phenyl radicals,alkylaryl radicals having from seven to 12 carbon atoms; preferably fromseven to l0 carbon atoms; aralkyl radicals having from seven to 12carbon atoms, preferably from from seven to 10 carbon atoms.

Representative non-limiting examples of useful phosphine materialsinclude triphenyl phosphine, trioctyl phosphine, tribenzyl phosphine andtritolyl phosphine.

The organic nitrogen bases useful in the present invention are generallydefined as aprotic and lack other polar functional groups, they includeclasses of compounds known as substituted pyridines, tertiary alkylamines, and tertiary alkylaryl amines. By substituted pyridines is meantany alkylated pyridine having the general formula:

wherein A -A, are monovalent radicals independently selected from thegroup consisting of hydrogen radicals and alkyl groups whose totalnumber of carbon atoms ranges from-one to 18. The termsubstitutedpyridine includes moieties such as 2, 4-, 6-trimethyl pyridine,2,6-ditertiary butyl pyridine, 2-methyl pyridine and the like. Bytertiary alkyl amines is meant compounds havingthe general formula,RR'R"N wherein R, R' and R" are independently selected from the groupconsistingtof alkyl radicals having from one to 10 carbonatoms,-preferably from one-to five carbon atoms and having at least sixcarbon atoms per nitrogen; tertiary alkylaryl amines are materialsrepresented by the generalformula ArRR'N wherein Ar is a substitutedaryl group having at least six carbon atoms and R and R have the abovedesignated meanings.

minor amounts is meant from 0.1 to 15 percent, preferably from 0.5 to 10percent based on-the number of moles of the complexing salt employed.Minor amounts of these additives are used to avoid excessive loss ofcomplexing capacity of thecomplexing salt and moreoversince minoramounts of said additives provide sufficient stability byloweringalkylation side reactions to a minimum. 1 I

The complexing solution may be generally described as low volatilityaromatic solvents-containing cuprous or silver complexing salts such asCuPF CuBR, CuBF,Cl,.CuAlCl -CuAlBr CuTaF. and CuAlCl,Br, where x y 4.These complexing solutions are more adequately described and set forthin copending appli cation Ser. No. 259,077, said application beingincorporated herein by reference. Additionally the use of thesecomplexing solutions in an olefin complexing process may be found incopending application Ser. No. 259,078, said application alsoincorporated herein by reference.

The temperatures and pressures at which the present invention isoperable are not critical and generally will range from about 20 to300C., preferably from 50 to 140C., and from 0.01 to 0.5 atmospheres toabout to 50 atmosphere pressure.

In a typical reaction scheme 4 mole triphenyl phosphine and 7 mole2,4,6-collidine are employed in a solution of CuAlCl, in 2.5 moles ofcumene. The solution absorbs ethylene reversibly from an ethylenecontaining feedstream while alkylation and other side reactions areminimized.

The present invention may be illustrated but is not necessarily limitedby the following examples.

EXAMPLE I 55.0g of a CuAlCl -methylbiphenyl-complex, 1.10g CuCl, 0.72gtriphenylphosphine and 0.53 g 2,6-di-tert.- butylpyridine are heated to140C. under a nitrogen atmosphere in a reaction vessel equipped withmagnetic stirrer, gas inlet and outlet. The input and output of gas aremonitored by means of two gas meters. Ethylene is introduced through atube ending shortly above the liquid level and a slow purge of gas ismaintained to avoid vapor locking. After the initial uptake of ethylenedue to complexing by the copper salt is complete, no further consumptionof gas can be observed over a period of 4% hours. An analogous runwithout the 2,6-di-tert.- butylpyridine showed continuous uptake ofethylene at a rate of 400 ml per hour per mole of copper. This showsthat 2,6-di-tert.-butylpyridine is able to suppress the alkylation sidereaction when used together with triphenylphosphine as additive.

EXAMPLE Ila 75.1 g CuAlCL-methylbiphenyl complex, 1.43g2,6-di-tert.-butylpyridine and 1.97g triphenylphosphine were heated to140C. under ethylene atmosphere. After 360 hours during which noalkylation was observable, a continuous uptake of ethylene could beobserved due to alkylation.

EXAMPLE Ilb 75.1g CuAlCh-methylbiphenyl complex and 1.43g 2,6-ditert.-butylpyridine were heated to 140C. under identical conditions asdescribed in Example lla, alkylation started after 232 hours.

Examples Ila an d llb clearly show that the combination of an organicphosphine and an organic nitrogen base is superior in terms of theduration of an olefin EXAMPLE III In this example, the rate ofalkylation was measured by saturating the complex with ethylene atatmospheric pressure and maintaining it under an ethylene atmosphere ina thermostated glass vessel connected to an oil-fitted wet-test meter,in such a way that any ethylene uptake following the initial saturationwould be recorded in the meter. The alkylation rate was expressed asmillimoles of ethylene per mole of CuAlCl, per hour.

In the first series of tests, runs in benzene at C. the alkylation ratein the absence of any additive varied from 9 to 25 units. Certainadditives reduced it slightly but substituted pyridine namely2,6-di-tertiary butyl pyridine and collidine 2,4,6-trimethylpyridinereduced it to immeasurably low values, below 0.02 units; the results ofthese runs are summarized in Table 1 below:

TABLE I STABlLlTY RUNS IN BENZENE' AT 509C.

Alkylation Time Concen- Rate mmoles on tration Cflmole CuAlCl, TestAdditive Mole on per hour Hours CuAlCl, None 0 25 2 9 I4 25 13.5Tributyl 1.57 7.8,7.2 16,5 Stibine Triphenyl 1.65 1.4 l6 PhosphineTriethyl 0.95 0.9,1.4 15.5, 5 Aluminum Di-t-butyl pyridine 6.9 0.02 207.6 0.1 15 Collidine 8.45 0.00 16 0.00 21 EXAMPLE IV The procedure ofExample 111 was repeated with a number of high boiling solvents attemperatures of up to 140C. Results of these runs are found summarizedin Table 11 below and show that the additives of the present inventionare equally effective even atthe higher temperatures. Note that in theabsence of any additive, alkylation rates of 18 and 46 units were ob-'tained even at temperatures as low as 50C. and C. The addition ofcollidine, arepresentative nitrogen base reduced the alkylation rates tozero at temperatures up to 140C. and at times up to 212 hours.-

Alkylation Time rate Cr/ 0n Temp. Cu/hr test Solvent Mole percentadditive C. X10 hrs- Cumene .6 Al Eta+aP 98 1.5 1 Blphenylehlorobiphenyl... 2.4 A1 B11s+sP 140 500 Diphenyl methane 2.4 A1 Bu: 13140 26, 47 5, 3 Methyl biphenyl 2.95 Al Bu -+1.83 mi N... 140 3.0, 3.424, 23 3,3 dimethyl bighenyl 6.38 Al E12: 3300 5 O-isopropyl bip enyl.2.5 A1 B113..-" 0,3 22 Cumene None 50, 75 18, 46 16, 44 Do 8-23Collidlne 100 0. 00, 0.00 15, 45 Do 7.0 collidine, 4 6 =P 100 0, 02 66Methyl biphenyl. 2-8 C011 ine 140 0.00 17 Do 6.6 Col1idine 140 0,00 212Do 4.5 Collidine +4.4 Ale; 140 0 0 3 1 Minutes.

EXAMPLE V In this example the solubility of pyridine AlCl complex iscompared to that of collidine AlCl in benzene solutions. To separateCuAlCh-benzene solutions was added sufficient amounts of pyridine andcollidine respectively. The precipitates formed were ana' lyzed for Cu,Al, Cl and C; the results of these analyzes are found below:

Additive: Pyri- Collidine dine '7: Cu 23.6 55.48 Al 7.57 0.0 Cl 47.842.2 C 14.82 1.45 Ratio Nitrogen Base/Cu 0.67 0.02 Ratio Al/Cu 0.76 0.0

The above data indicate that pyridine causes sizable amounts of organicbase to form in the precipitate and equal amounts of Al and organic baseshowing that the precipitate is CuCl Base: AlCl; adduct. This in turnmeans that pyridine is ineffective as an inhibitor since it is removedfrom the aromatic solution and therefore cannot neutralize the HClproton donor material. With collidine, little aluminum or base ispresent in the precipitate which is mostly CuCl with the Base: A'lCladduct remaining in solution and able to react with'HCl to therebyminimize alkylation of the solution.

What is claimed is:

1. An improved process for the separation and recovery of complexibleolefins from olefin-containing feedstreams by contacting saidfeedstreams with an aromatic sorbent solution containing cuprous saltswhose anionic components are Lewis acids wherein the improvementcomprises incorporating into said aromatic sorbent solution a minoramount of an organic phosphine in combination with an organic nitrogenbase material selected from the group comprising alkyl amines, tertiaryalkylaryl amines and substituted pyridines, to thereby substantiallyreduce alkylation and polymerization side reactions and stabilize saidaromatic sorbent solution.

2. The process of claim 1 wherein said organic phosphine has the generalformula R,R,R,P wherein R R,, and R are monovalent radicalsindependently selected from the group consisting of alkyl radicalshaving from one to carbon atoms, phenyl radicals, alkylaryl radicalshaving from seven to 12 carbon atoms and aralkyl radicals having fromseven to l2 carbon atoms.

3. The process of claim 1 wherein said organic nitrogen base material isan alkyl amine having the general phenylphosphine,

formula: RR'R"N wherein R, R, and R" are independently selected from thegroup consisting of alkyl radicals having from one to 10 carbon atoms.

4. The process of claim 1 wherein said organicnitrogen base material isa substituted pyridine having the general formula:

wherein A A are monovalent radicals independently selected from thegroup consisting of hydrogen radicals and alkyl groups whose totalnumber of carbon atoms ranges from one to 18.

5. The process of claim 1 wherein said organic nitrogen base material isa tertiary alkylaryl amine having the general formula ArRRN wherein Aris a substituted aryl group having at least six carbon atoms; R, and Rare independently selected from the group consisting of alkyl radicalshaving from one to 10 carbon atoms.

6. The process of claim 1 wherein from 0.1 to 15 percent of said organicphosphine and organic nitrogen base material, based on number of molesof complexing salt, is present in said aromatic sorbent solution.

7. The process of claim 1 wherein said complexible olefins to berecovered are ethylene and propylene.

8. The process of claim 1 wherein said contacting is carried out attemperatures in the range of from about 20 to 300C. and pressuresranging from 0.5 to about 50 atm.

9. The process of claim 1 wherein said cuprous salt is one selected fromthe group consisting of CuPF CuBF CuBF,,Cl, CuAlCl CuAlBr CuTaF, andCuAlCl,Br,, wherein x y are integers whose sum equals 4. i I

10. The process of claim 1 wherein said organic nitrogen base is oneselected from the group consisting of 2,4,6-trimethyl pyridine,2,6-ditertiary butyl pyridine, 2,6-diethyl N,N-diethyl amine. v

l 1. The process of claim 1 wherein said organic phosphine is oneselected from the group consisting of tritrioctylphosphine,tribenzylphosphine and t'ritolylphosphine.

aniline and tributyl

2. The process of claim 1 wherein said organic phosphine has the generalformula R1R2R3P wherein R1, R2, and R3 are monovalent radicalsindependently selected from the group consisting of alkyl radicalshaving from one to 20 carbon atoms, phenyl radicals, alkylaryl radicalshaving from seven to 12 carbon atoms and aralkyl radicals having fromseven to 12 carbon atoms.
 3. The process of claim 1 wherein said organicnitrogen base material is an alkyl amine having the general formula:RR''R''''N wherein R, R'', and R'''' are independently selected from thegroup consisting of alkyl radicals having from one to 10 carbon atoms.4. The process of claim 1 wherein said organic nitrogen base material isa substituted pyridine having the general formula:
 5. The process ofclaim 1 wherein said organic nitrogen base material is a tertiaryalkylaryl amine having the general formula ArRR''N wherein Ar is asubstituted aryl group having at least six carbon atoms; R, and R'' areindependently selected from the group consisting of alkyl radicalshaving from one to 10 carbon atoms.
 6. The process of claim 1 whereinfrom 0.1 to 15 percent of said organic phosphine and organic nitrogenbase material, based on number of moles of complexing salt, is presentin said aromatic sorbent solution.
 7. The process of claim 1 whereinsaid complexible olefins to be recovered are ethylene and propylene. 8.The process of claim 1 wherein said contacting is carried out attemperatures in the range of from about 20* to 300*C. and pressuresranging from 0.5 to about 50 atm.
 9. The process of claim 1 wherein saidcuprous salt is one selected from the group consisting of CuPF6, CuBF4,CuBF3Cl, CuAlCl4, CuAlBr4, CuTaF6 and CuAlClxBry wherein x + y areintegers whose sum equals
 4. 10. The process of claim 1 wherein saidorganic nitrogen base is one selected from the group consisting of2,4,6-trimethyl pyridine, 2,6-ditertiary butyl pyridine, 2,6-diethylN,N-diethyl aniline and tributyl amine.
 11. The process of claim 1wherein said organic phosphine is one selected from the group consistingof triphenylphosphine, trioctylphosphine, tribenzylphosphine andtritolylphosphine.